1. Field of The Invention
The invention relates to an arrangement for verifying a playing authorization for a reproduced encrypted information signal reproduced by a reproducing device cooperating with the arrangement, and for supplying a decrypted information signal when a playing authorization is available, the arrangement comprising verification means for receiving a reproduced encrypted information signal and for supplying key information suitable for correctly decrypting the reproduced encrypted information signal when a playing authorization is available, and decryption means for receive key information and for decrypting the reproduced encrypted information signal when suitable key information is available.
2. Description of The Related Art
An arrangement of the type defined in the opening paragraph, is known, for example, from International Patent Application WO 96/05700 A1, corresponding to U.S. Pat. No. 5,640,453.In the known arrangement, which is formed by a so-called set-top box, the verification means enables identification information contained in a reproduced encrypted information signal to be determined. When such identification information is present, a playing authorization for the reproduced encrypted information signal is obtained. The identification information contains the key information which can be supplied to the decrypting means in order to decrypt the reproduced encrypted information signal. A reproduced decrypted information signal can be displayed by means of a television set which can be connected to the known arrangement.
The known arrangement is adapted to record characteristic playing information which characterizes the number and length of playing events of a decrypted information signal in the case of a playing authorization. Furthermore, by means of a data link, the known arrangement is connected to a broadcasting station which forms a play interrogation device. By interrogating the characteristic playing information recorded by the known arrangement, the play interrogation device can determine how many times and for how long an encrypted paid-service information signal reproduced by the playing device has been decrypted in the known arrangement and has, consequently, been used by the user of the known arrangement. Charging for the usually repeated reproduction of paid-service information signals can be effected on the basis of the characteristic playing information.
However, with regard the known arrangement, it has appeared that the presence of encrypted identification information in the reproduced encrypted information signal, this identification information allowing a correct decrypting of an encrypted information signal and being necessary for the correct operation of the known arrangement, has been used by unauthorized persons for making illegal copies which contain the information signal that has already been decrypted. Record carriers with decrypted information signals have been sold by persons not authorized to do so, resulting in substantial financial damage for broadcasting stations.
Moreover, when the characteristic playing information recorded with the known arrangement is interrogated by a play interrogation device, the problem arises that the play interrogation device initially has no information whether and where there is a known arrangement by means of which paid-service information signals, for which the collection of charges is effected by the play interrogation device, are reproduced. This considerably complicates the collection of charges for the reproduction of paid-service information signals.
Furthermore, it is not possible to rule out that the characteristic playing information recorded by the known arrangement is changed by a person not authorized to do so, which additionally complicates the collection of charges.
Moreover, with regard to the known arrangement, it has been found that, on the one hand, interrogating the characteristic playing information recorded by means of the known arrangement at comparatively long time intervals, will result in uncertainty for the user of the known arrangement as to the amount of the charges and, on the other hand, interrogating the characteristic playing information recorded by means of the known arrangement at comparatively short time intervals will result in a comparatively large expense for the broadcasting station.